The present invention relates to an agricultural mower having a cutter bar of the type used in mowing hay or other forage crops. More specifically, it relates to an arrangement of the cutter assembly and its suspension.
Hay mowers are large machines which in use travel at fairly high ground speeds. As used herein, the term "hay mowers" is intended to be broad enough to include a large range of agricultural mowing equipment. For example, some manufacturers call them mower/conditioners, or "haybiners". Mowers are generally pulled by a tractor. The mower is located to the side so that the tractor operates in a swath already cut and does not mat the hay into the ground. Whether the crop is standing upright or fallen over and matted by the weather, it hides most obstacles from sight. Thus, the size and speed of operation, the remoteness of the cutter from the operator and the tendency of the crop to hide obstacles, all make it difficult for the operator to see potential obstacles or immediately to notice any damage which may occur.
Although some agricultural mowers use rotary cutting blades, the present invention uses a sickle bar cutter because I find it more desirable in recovering more of the nutritious elements of the crop, particularly when the crop is matted or "lodged" as it is sometimes called. The cutter blades of a sickle bar act like scissors in that a horizontally extending blade forms a "V" with a guard member so that when the blade is reciprocated it cuts the hay at its base in a scissors-like action. To reduce the possibility of damage to the blade, an elongated point or "guard" is mounted adjacent each section or cutting edge of the blade and projects in front of the horizontal cutter blade. The guards are normally more sturdy and serve to separate the stems of the plants while guiding the separated stems into the cutters, and to protect the cutter mechanisms themselves by engaging obstructions before the cutting edges encounter them. A number of such guards are mounted side-by-side and, together with the blades are collectively referred to as a "cutter bar".
As the apparatus traverses a field, the cutter blade is continuously reciprocated within the guard by a common power drive mechanism. If the cutter blade were to strike an obstacle, such as a rock, not only would it damage that particular cutting mechanism, but if the damage were such as to bend the cutter blade, it could prevent proper operation of the entire cutter bar. Because the cutter bar is located remotely from the operator, the damage may go unnoticed for some time. It is, therefore, very important to prevent damage to the cutter bar assembly.
Hay crop, after it has matured, tends to become matted under its own weight against the ground. One reason for desiring to cut hay as close as possible to the ground is that valuable elements of nutrition are believed to be present in the base of the stem of the plant. It is difficult to harvest all of the crop that is desired when hay is lodged because conventional cutter bars have the blade and guards horizontal. Thus, the cutter engages the base of the plant at an acute angle rather than perpendicular. The reason cutter bars are horizontal is that they are suspended by a mechanism which includes a pivot which is located almost directly behind the guard. Thus, when the point strikes an object, it rotates (when viewed from the right) like the hand of a clock going from the six o'clock to the five or four o'clock positions. If the hay mower is operated with its cutter blades located very close to the ground another problem arises. The lower the cutter bar is located, the greater the possibility that the cutter will engage rocks or other obstacles.
To reduce damage to the cutter bar in the above-mentioned prior commercial hay mowers, the cutter bar was permitted to rotate upwardly and then rearwardly out of the normal use position when the guards engaged an obstruction. However, such conventional designs mounted the entire header assembly (which includes the cutter bar, drive shaft and frame) between side plates which define a rigid structure typically seven to twelve feet long and of considerable weight. As mentioned, the header assembly was mounted so that it pivoted about a transverse axis located at appoximately the same height as the guards, but behind them, so that when the guards strike an obstruction, the header assembly rotates clockwise upwardly and away from the obstruction, as represented schematically in FIG. 5.
Because the pivot axis for the cutter bar is behind the bar itself, a substantial impact force is normally encountered before the header assembly will respond. At normal operating speeds, this has the tendency to damage the header even if it is spring-biased, particularly if the obstacle struck has an upright surface. It will be observed that the initial movement of the prior art cutter when it hits an object is upward. Any rearward movement is slight at first because of the location of the pivot. Due to the size and weight of the header and the high ground speeds, damage can and does occur.
In U.S. Pat. No. 3,063,226 issued to E. M. Pfauser, there is disclosed a riding type rotary mower having the housing of a rotary cutting unit suspended beneath the mower by means including a parallel linkage arrangement. The mower is capable of traversing uneven terrain, and for this purpose, runners are provided at the edges of the housing to lift the cutter housing when a runner rides over a mound. The drive shafts to the rotary mower blades are provided with splines so that as the housing raises, the drive shafts telescope. Also, the axes of the links of the parallel suspension linkage are set at an angle with the vertical of approximately 70.degree. which permit slight rearward movement of the cutter housing as the housing raises.
The runners at the sides of the cutter housing do not ordinarily touch the ground but in normal operation are held at a predetermined height from the ground. Damage to the cutting unit is avoided if an obstacle in the path of the mower is engaged by the runner allowing it to lift the cutting unit over the obstacle. However, the runners would be ineffective to lift the cutting unit if the forward vertical wall of cutter housing were to strike an object, such as a rock, having a substantially vertical wall itself and having a height extending, for example, to the mid-point of the cutter housing.
The suspension mechanism of the rotary mower structure disclosed in the referenced patent is designed to elevate the cutter unit rather to displace it rearwardly because the couplings and the linkage accommodate only slight rearward movement. Thus, upon striking an obstacle, such as a rock, with a part of the cutter housing other than the runners, the cutter housing would respond substantially in the manner of the conventional rear-pivotted cutter bar assemblies.